WO2012034543A1 - Structural connector for bamboo - Google Patents

Abstract

A structural connection device for structural elements in the form of a solid or closed section bar and of substantially circular form, typically bamboo, is characterized in that it is composed of two plates provided with various orifices or grooves for affixing additional structural elements placed in a diametrically opposing position on the outer surface of said bar, said plates being joined together by means of one or more threaded bars or bolts with the respective washers and nuts thereof, which diametrically traverse said bar through one or more holes previously made in said bar, pressing said plates against the surface of said bar. Said bolts in turn incorporate springs or a flexible connector for absorbing the dimensional variation in bamboo.

Description

 "STRUCTURAL CONNECTOR FOR BAMBOO"

 Technology sector

 The present invention is related to the construction sector in general, structures not limited to walls, floors, skies or ceilings (International Classification E04B1 / 18), specifically in the sector of structures comprising elongated load bearing elements, as per example columns, beams, trusses and the like (International Classification E04B1 / 18) and more specifically the connections between structural elements (International Classification E04B1 / 18B). The present invention is especially designed for structures with bamboo bearing elements, although not limited to these (International Classification E04B 1/26), more specifically connections specially adapted for these structures (E04B1 / 26B).

 The connection sector for structures in general is also applicable, for construction elements in the form of a closed section bar (E04B1 / 58C) and of substantially circular shape (E04B1 / 58C2), with separate connection devices (E04B1 / 58C2C).

Background of the invention

 The field of bamboo construction presents an important technical challenge in the manufacture of joints. Said joints should be as light as possible at the same time and offer the greatest capacity for load transmission without becoming a weak or breaking point in the bamboo cane.

There are currently a variety of unions of this type, as described for example in the studies carried out by Caori P. Takeuchi. One of them is that of the Simón Vélez type, which consists of a threaded rod through several rods and pressed at its ends against the set of rods using nuts and washers. The cells crossed by said bar are filled with mortar in order to reinforce them. A joint is considered too heavy and its resistance is relatively low.

Another type of known joint, which can be called a mechanical joint, which also consists of a threaded rod, with the difference that instead of being filled with mortar, the reeds are reinforced in their holes by sheets, plates or perforated and nailed or screwed washers on the bamboo surface. It has the advantage of being lighter but its resistance is much lower. This variant is also used without plates or washers by tying the reeds with wire, leather strips or rope, which over time become loose. Another type of union is with mortar and rods. In this joint, in addition to the mortar filling, a series of rods is introduced through the cell where the joint is made, in order to improve the reinforcement. It offers better resistance but is more expensive and heavy than those described above.

Another type of joint is known as clamp connection. In this type of joint, a sheet of metal is wound around the surface of the rods to be joined, near or around the point where the rod is drilled to produce a union of the mechanical type already described. The clamp is fixed to the rod by a plurality of screws. This reinforcement makes it possible to build a relatively light and much stronger joint than the previous ones. However, it is of artisanal construction, relatively slow and subject to error.

 Another type of union, known as union with plates, consists of screwing wide plates on both sides to a set of rods that go to said plates. These joints are considered heavy and expensive due to the structural capacity required in the plates, apart from the fact that their resistance is not much higher than that of the mechanical joints. Unlike the previous unions, it allows the axial axes of the rods to be on the same plane, which contributes to a more balanced handling of the loads.

All the joints described above have the disadvantage that they are applied to a unique form of connection between the rods, so that in order to add different types of construction elements it would be necessary to consider other types of joints. In order to achieve a more uniform construction system, it would be desirable to have a more versatile or universal type of joint.

 Patent DE 3817236 discloses an advance in this regard, by providing a joint of the clamp type split into two semi-cylindrical sections, which are joined together by means of screws to hold the rod and provide separately bases for the connection of additional construction elements, since be reeds provided with the same type of connector or elements of other types.

 However, this connector is designed for rods or rods of circular section with very uniform dimensions and is too rigid. By fully hugging the reeds does not admit variations in the dimensions of the different reeds, nor own and natural variations of the reed throughout its useful life.

In addition to the limitations already described, all joints shown lack the ability to automatically and safely adjust to dimensional variations during the useful life of the structure, such as the shrinkage of the bamboo cane.

 Brief description of the drawings

 The included drawings show the best way to carry out the invention as well as examples of several other possible embodiments of the invention.

 Figure 1 shows a first embodiment of the invention with the bar in section view. Figure 2 shows a second embodiment of the invention with the bar in section view. Figure 3 shows orthogonal views of the plate element for a first embodiment of the invention.

Figure 4 shows orthogonal views of the plate element and its cover for an alternative embodiment of the invention.

 Figure 5 shows orthogonal views of the plate and a spring bolt installed between the plate and the bolt in alternative embodiments of the invention.

 Description

The present invention provides a joint system for circular section bars, typically of bamboo, composed of two base plates, a flexible connector installed inside the bar and a pair of bolts that press said plates against said flexible connector. In this way a universal connection is provided, in the sense that it can not only accept through said base plates the interconnection of bamboo bars, but also the union of other construction elements of various types. The shape of the plates allows connecting to rods of various diameters within a typical range of sizes. The flexible connector allows to absorb the dimensional variations characteristic of the construction with bamboo and also to limit its extension in case of excessive loads.

Detailed description

The area of application of this invention is that of connections for structures in general, for construction elements in the form of a closed section bar and of substantially circular shape, particularly bamboo pieces. Within said area, it refers specifically to the type of connections that fix one or more universal bases to each bamboo bar, which are joined together to connect with other bars or with other elements by means of additional connection devices.

An improvement provided by the present invention is to provide a universal joint, which can connect both structural elements provided with said joint, like any other type of element that can be coupled with the base surface offered by said joint. Furthermore, said joint provides a flexible clamping system, which absorbs the dimensional variations that may occur in the bar, such as those produced by the natural shrinkage of bamboo. Said tightening system is configured in such a way that the flexible elements operate in compression, so that in case of an excessive load they will deform until they reach their maximum compression, from which point their resistance to the applied load becomes substantially higher.

 In a preferred form of the invention, the joint consists of two base plates (1A, IB), a flexible connector (2) and two bolts (3 A, 3B) that join the base plates (1A, IB) with the flexible connector (2) and press them against the surface of the bamboo bar (4) to fix it. However, this does not exclude the possibility of using expanded plates, which are connected to each other by two or more sets of connectors and bolts.

 In said preferred form of the invention, the plates (1A, IB) have various perforations or grooves (11) provided for fixing additional structural elements. Said plates (1A, IB) are located in a diametrically opposite position with respect to each other on the external surface of the bar (4). On their outer face these plates (1A, IB) offer a flat surface (12), in order to facilitate the fixation of other structural elements by means of the perforations or grooves mentioned (11), while on their inner face they offer a surface concave (13), which adapts to a typical range of bar diameters (4), for example the type of bars used in bamboo construction. The plates (1A, IB) can also have bent edges towards the outside of their concave surface (13) and cut in the form of teeth or serrations, which are embedded in the surface of the bar (4) when pressed against it. This does not exclude the possibility of alternative ways of producing a serrated or rough surface to improve the friction of the plates against the surface of the bar (4).

In a preferred form of the invention, the flexible connector (2) is in the form of an elongated cylindrical capsule. Said capsule can be formed, for example, from a tube whose edges have been deformed to reduce its diameter at the ends (21 A, 2 IB). This form does not exclude the possibility that the connector has lateral openings in order to facilitate the handling and installation of the other elements that compose it. At inside said connector (2), there are two springs (5A, 5B), one resting against each of its ends of reduced diameter (21 A, 2 IB).

 In the preferred configuration, the connector (2) is placed inside a diametral perforation (41A, 41B) previously practiced in the bar (4), and the plates (1A, IB) are placed on the external surface (42) of the bar, one at each end of said perforation (41 A, 4 IB). Each of the bolts (3A, 3B) passes through the corresponding plate (1A, IB) and is inserted into the flexible connector (2) through each of its ends (21 A, 2 IB) until it crosses each of the springs ( 5 A, 5B). On the tip of each bolt (3A, 3B) protruding from the end of each spring (5A, 5B) near the center of the connector (2), a nut (6A, 6B) and its corresponding washer (7 A, 7B) to tighten the assembly by turning either the nuts (6A, 6B) or the bolts (3A, 3B).

 In an alternative configuration the connector contains only a helical spring (5 A), which rests against the edge of reduced diameter (21 A) of one of the connector ends and is tightened with a bolt (3 A). The bolt on the opposite side (3B) pulls the connector (2) using the corresponding nut (6B) and washer (7B), resting directly on the end of reduced diameter (2 IB).

 In another alternative configuration, the plates (1A, IB) contain a second flat surface (14) hidden under the external flat surface (12), on which the bolt heads (3A, 3B) can be supported so that they are also hidden. In addition, a cover (8, 8A, 8B) can be added, which can help reinforce the plate (1A, IB) and cover the bolt heads (3A, 3B).

 In another alternative configuration, the flexible connector is not used. Instead, a single bolt (3) is used which from one of the plates (1A) to the opposite plate (IB). In order to sustain the tightening in case of a dimensional variation in the bar, the springs (5 A, 5B, 9A) are placed between the bolt head (3) and the plate or between the bolt nut (3) and the plate (1A, IB).

 In another alternative configuration, in order to improve the support of the springs (5 A, 5B), each end of the connector (21 A, 2 IB) has a washer (22 A, 22B) as a cover, so that the Springs (5 A, 5B) are pressed against said washers (22A, 22B).

As a complement to the preferred form, bushings can be placed around the bolts (3A, 3B), adjacent to the plates (1A, IB), so that these bushings prevent direct contact of the bolts (3 A, 3B) with the perforation walls (41 A, 4 IB) on the bar (4). These preferred forms of the invention do not exclude the possibility of using other types of springs compatible with the described connector, for example in the form of one or more conical washers (9A). Nor is it possible to dispense with the flexible connector, in which case the plates (1 A, IB) are pressed against the bar by a single bolt that goes directly from one of the plates (1A) to the opposite plate (IB).

Claims

Claims  1. A device for the structural connection of construction elements in the form of a closed or solid section bar and of substantially circular shape, characterized by being composed of two plates provided with various perforations or grooves located on one or more flat faces provided for fixing of additional structural elements on one of its sides and of a concave face on the opposite side whose curvature is similar to the external curvature of said bar, said plates located diametrically opposite position on the external surface of said bar and joined together by one or more bolts or threaded bars with their respective washers and nuts, which diametrically traverse said bar through one or more holes and press said plates against the surface of said bar.  2. The device of claim 1 characterized in that the plates have on the concave face in contact with the bar a plurality of teeth-shaped protrusions, which penetrate the surface of said bar when pressed against it. 3. The device of claim 1 or 2 characterized in that at least one of the bolts that press the plates against the bar has at least one of its ends a spring that is compressed by tightening said bolt.  4. The device of claim 1 or 2 characterized in that the element that joins and presses said plates against the bar is formed by:  to. At least one tubular element located inside the hole made in the bar, whose edges have been deformed to reduce the inside diameter at its ends.  b. A spring located within said tubular element, whose outer diameter is such that it is retained by the narrowings at the ends of said tubular element. C. A first bolt whose head rests on a first plate located on the surface of the bar and extends to the inside of the tubular element, passing inside the spring until connected with a nut and washer assembly to clamp said spring against the narrowing of the tubular element closest to the first plate. d. A second bolt whose head rests on the second plate and extends to the inside of the tubular element to connect with a nut and washer as required, imprisoned inside said tubular element by the narrowing in the diameter opposite to the one that imprisons the spring.  5. The device of claim 4, characterized in that the tubular element contains a second spring in its interior similar to the first, each spring pressed against one end of said tubular element by means of a nut and washer connected by means of a bolt whose head rests on each of the plates located on the outer surface of the bar.